The present invention relates to a refractory submerged feeder nozzle for discharging and injecting steel into a mold for continuous casting.
It is customary to feed steel from a tundish, ladle or the like into a casting mold by means of a pipe like feeder nozzle. This pipe runs the molten metal through the surface of the steel bath in the mold and here particularly through the layer of casting powder and slag covering that surface, deeper into the bath itself. The known feeder pipes consist of refractory material such as pure, amorphous silica or graphite treated material that contains alumina. In other cases, one has used zirconium-silicate and other highly fire proof materials. U.S. Pat. No. 3,517,726 is representative of this state of the art.
It has been found that such feeder nozzles produce certain deposits in the mold right in the beginning of casting. The cause for this formation is to be seen in the high temperature differential between the molten steel and the pipe having a very high thermal conductivity. The use of glazed feeder pipes reduces but does not eliminate the formation of such deposits.
Another problem is the erosion of the feeder pipe particularly in the zone of contact with the rather aggresive powder slag. The wear resulting therefrom is more extensive than the wear of the pipe on account of the molten steel. The particular erosion weakens the feeder locally, causing it to break sooner or later. It has been suggested to skirt the feeder in the slag range by means of a fire proof annulus, which is an exchangeable piece and has but a small distance from the feeder; see for example German printed patent application No. 20 42 897. Impeding the slag aggression has also been tried by chosing an elliptical, outer cross-sectional contour of the pipe (see German printed patent application No. 23 58 339) and the casting flow is internally guided along the major axis of the ellipse.